Hot melt adhesive

ABSTRACT

A hot melt adhesive material and articles made using the hot melt adhesive to assemble structures in an article. The adhesive material typically is manufactured by blending amorphous polymer with a heterophase polymer having crystallinity into an adhesive composition.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.13/836,385, filed on Mar. 15, 2013, which claims the benefit of U.S.Provisional Application No. 61/702,950, filed on Sep. 19, 2012, all ofwhich are hereby incorporated by reference.

Disclosed is a general purpose hot melt adhesive material that can beapplied to substrates such as cellulosic materials, film, fiber ornonwovens in the construction of articles. The adhesive composition ismanufactured to obtain melt viscosity, cohesion and adhesion sufficientto assemble an article and obtain a mechanically stable product. Theadhesive typically comprises a blend of polymer materials combined atproportions that obtain the desired and useful construction propertiesuseful in the manufacture of articles. One embodiment is the hot meltadhesive. A second embodiment is an article manufactured using theconstruction properties and aspects of the hot melt adhesive.

Common hot melt adhesives are made by combining polymer and additivecomponents in a substantially uniform thermoplastic blend. Improvedmaterials are needed for use in improved application equipment and incurrent and updated article constructions. A substantial need exists inproviding new formulation combinations of materials and blendingtechniques that obtain improved adhesives.

The adhesive composition comprises a first amorphous polymer and asecond heterophase polymer. The amorphous polymer comprises an amorphousor random polymer comprising an alpha olefin co-polymer comprising majorproportion of propene. The second polymer comprises a heterophase alphaolefin-co-polymer having amorphous character and at least somesubstantial crystalline content. The crystalline content can be in theform of one or more polymer blocks or sequences that are stereoregular.In one embodiment, these sequences or blocks are substantiallycrystallizable sequences or blocks.

As used herein “homopolymer” means a polymer resulting from thepolymerization of a single monomer, i.e., a polymer consistingessentially of a single type of repeating unit.

As used herein, the term “copolymer(s)” refers to polymer(s) formed bythe polymerization of at least two different monomers. For example, theterm “copolymer” includes the copolymerization reaction product of amonomer such as propene or butene, preferably 1-butene and analpha-olefin, such as for example, ethylene, 1-hexene or 1-octene.

As used herein, the term “propene copolymer” or “propylene copolymer”means a copolymer of greater than 40 or 50 wt. % or more propene and atleast one monomer selected from the group including ethylene and a C₄ toC₂₀ α-olefin.

As used herein, the term “butene copolymer” means a polymer of n-butene(1-butene) or 2-butene and at least one monomer selected from the groupof C₂₋₃ and C₅₋₂₀ alpha olefins. Butene copolymers typically comprise aminimum amount at least about 40 or about 50 wt. % or more of a butenemonomer such as 1-butene.

The term “heterophase” polymer means a polymer having an amorphouscharacter and at least some substantial crystalline content (at least 5wt. %, 10 wt. %, 20 wt. %, 40 wt. % or 50 wt. % crystalline content)that can provide cohesive strength in the cooled adhesive mass. Thecrystalline content can be in the form of stereoregular blocks orsequences.

The term “amorphous” means the substantial absence of crystallinity,(i.e.) less than 5% and less than 1%.

The term “sequence or block” means a polymer portion of repeatingmonomer that is similar in composition, crystallinity or other aspect.

As used herein, the term “open time” means the amount of time elapsedbetween application of a molten hot melt adhesive composition to a firstsubstrate, and the time when useful tackiness or wetting out of theadhesive on a substrate effectively ceases due to solidification of theadhesive composition. Open time is also referred to as “working time.”

As used herein, the term “substrate” means any item having at least apartially or fully solidified fiber or planar surface with which contactwith a hot melt adhesive composition is intended. In some cases the samearea, circle, bead, line, filament or dot of hot melt adhesivecomposition is contacted with two or more substrates for the purpose ofcreating an adhesive bond there between. In some such cases thesubstrates are part of the same item: for example, folded film or foldednon-woven, two sides of a cardboard sheet folded over, wherein the twosides are adhesively bonded together. In other such cases the substratesare part of different items: for example, a plastic film that isadhesively bonded to a non-woven or cardboard sheet. The substrates canbe impermeable, permeable, porous or nonporous.

As used herein, the term “substantially” means generally the same oruniform but allowing for or having minor fluctuations from a definedproperty, definition, etc. For example, small measurable or immeasurablefluctuations in a measured property described herein, such as viscosity,melting point, etc, may result from human error or methodologyprecision. Other fluctuations are caused by inherent variations in themanufacturing process, thermal history of a formulation, and the like.The adhesive compositions of the, nonetheless, would be said to besubstantially having the property as reported.

As used herein, the term “major proportion” means that a material ormonomer is used at greater than 50 wt. %. As used herein, the term“primary component” means that a material or monomer is the more commonsubstance or has the higher concentration in the mixture or polymercompared to others but may not be as much as 50 wt. %.

The adhesive material comprises a first polymer comprising a polyolefincomprising a substantially amorphous or randomly polymerized polymermaterial and a second polymer comprising a heterophase polymer.

The first amorphous polymer comprises typically butene (e.g.) 1-buteneand can contain ethylene, propene or a second C₄₋₄₀ olefin polymer.These substantially amorphous low crystallinity polymers have less than10% and preferably less than 5% crystalline character.

The second heterophase olefin polymer comprises a first poly alphaolefin polymer comprising a substantial proportion (greater than 40 or50 mole %) of a propene monomer and comprises an amorphous polymer withsome crystalline content.

The amorphous polymer is a butene-based copolymer (the minimum amount isat least about 30 or 40 or 50 wt. % of 1-butene), which may also bereferred to as a random butane-α-olefin copolymer. The butene copolymerincludes one or more units, i.e., mer units, derived from propene, oneor more comonomer units derived from ethylene or α-olefins includingfrom 4 to about 20 carbon atoms.

The first copolymer comprises about 30 mole %-about 70 mole %,preferably about 40 mole % to about 60 mole % of units derived frombutene. In addition to butene-derived units, the present copolymercontains from about 70 mole %-about 30 mole % to about 60 mole %-about40 mole %, of units derived from preferably ethylene, propene or atleast one C_(5 to 10) alpha-olefin monomer.

In one or more embodiments, the alpha-olefin comonomer units can also bederived from other monomers such as ethylene, 1-butene, 1-hexane,4-methyl-1-pentene and/or 1-octene. Exemplary alpha-olefins are selectedfrom the group consisting of ethylene, butene-1,pentene-1,2-methylpentene-1,3methylbutene-1,hexene-1,3-methylpentene-1,4-methylpentene-1,3,3-dimethylbutene-1,heptene-1, hexene-1, methylhexene-1, dimethylpentene-1,trimethylbutene-1, ethylpentene-1, octene-1, methylpentene-1,dimethylhexene-1, trimethylpentene-1, ethylhexene-1,methylethylpentene-1, diethylbutene-1, propylpentane-1, decene-1,methylnonene-1, nonene-1, dimethyloctene-1, trimethylheptene-1,ethyloctene-1, methylethylbutene-1, diethylhexene-1, dodecene-1, andhexadodecene-1.

In one or more embodiments, amorphous copolymer comprises about 30 mole%-about 70 mole %, preferably about 40 mole % to about 60 mole % ofunits derived from butene and from about 70 mole %-about 30 mole % toabout 60 mole %-about 40 mole %, of units derived from at least onealpha-olefin monomer selected from ethylene, propene, 1-hexene or1-octene. Small amounts of α-olefin monomer(s) can be used in the rangeof about 0.1 to 20 mole %. The amorphous polymer has a weight averagemolecular weight (Mw) of about 1,000 to about 25,000 or less, preferablyabout 2,000 to 20,000.

In one or more embodiments, first copolymer comprises about 30 mole%-about 70 mole %, preferably about 40 mole % to about 60 mole % ofunits derived from butene and from about 70 mole %-about 30 mole % toabout 60 mole %-about 40 mole %, of units derived from propene, whilesmall amounts of α-olefin monomer(s) can be used in the range of about0.1 to 20 mole %.

The amorphous polymer has a weight average molecular weight (Mw) ofabout 1,000 to about 50,000 or less, preferably about 5,000 to 45,000.

The amorphous copolymer has a viscosity of less than 10,000 mPa·s (1centipoise [cps]=1 mPa·s), for example about 2000 to 8000 mPa·s, whenmeasured by ASTM D3236 at 190° C. Melt Viscosity was determinedaccording to ASTM D-3236, which is also referred to herein as“viscosity” and/or “Brookfield viscosity”.

Some examples of amorphous polyolefin include the Rextac polymers madeby Huntsman including Rextac E-63, E-65, 2815, 2830. etc. See, forexample Sustic, U.S. Pat. No. 5,723,546 for a description of thepolymers and which is expressly incorporated herein. Other usefulamorphous polymers are sold as Vistoplast® and Eastoflex® materials.

The adhesive material comprises a second polyolefin comprising asubstantially heterophase copolymer. The heterophase polyolefin maycomprise a propene copolymer (i.e.) propene-based polymer with othercomonomer(s). The propene-based polymer backbone preferably comprisespropene and one or more C₂ or C₄₋₂₀ α-olefins. The propene-basedheterophase polymer, for example, may comprise propene and ethylene,hexene or optionally other C₂ or C₄₋₂₀ α-olefins. The polymer comprisesabout 99.5 to about 70 wt. %, preferably about 95 to about 75 wt. % ofunits derived from propene. In addition to propene derived units, thepresent copolymer contains from about 0.1 to 30 wt. % preferably fromabout 5 to 25 wt. %, of units derived from preferably at least C₂₋₄ or aC₅₋₁₀ alpha-olefin.

In one or more embodiments, the second copolymer comprises a majorproportion of propene and about 0.1 to 30 wt. %, or 2 to 25 wt. %ethylene. In one or more embodiments, the second copolymer comprises amajor proportion of propene and about 0.1 to 30 wt. or 2 to 25 wt. %1-butene.

In one or more embodiments, the second copolymer comprises a majorproportion of propene and about 0.1 to 30 wt. %, or 2 to 25 wt. %1-hexene. In one or more embodiments, the second copolymer comprises amajor proportion of propene and about 0.1 to 30 wt. %, or 2 to 25 wt. %1-octene.

Other comonomer for use in either the first or second polyolefincomprise ethylene or α-olefins containing 4 to 12 carbon atoms.Exemplary α-olefins may be selected from the group consisting ofethylene; 1-butene; 1-pentane; 2-methyl-1-pentene; 3-methyl-1-butene;1-hexene-3-methyl-1-pentene-4-methyl-1-pentene-3,3-dimethyl-1-butene;1-heptene; 1-hexene; 1-methyl-1-hexene; dimethyl-1-pentene;trimethyl-1-butene; ethyl-1-pentene; 1-octene; methyl-1-pentene;dimethyl-1-hexene; trimethyl-1-pentene; ethyl-1-hexene;1-methylethyl-1-pentene; 1-diethyl-1-butene; propyl-1-pentene; 1-decene;methyl-1-nonene; 1-nonene; dimethyl-1-octene; trimethyl-1-heptene;ethyl-1-octene; methylethyl-1-butene; diethyl-1-hexene; 1-dodecene and1-hexadodecene. Preferred C₄₋₁₀ alpha-olefins are those having 6 to 8carbon atoms, with the most preferred alpha-olefin being 1-hexene and1-octene.

Preferred propene copolymers are copolymers wherein the comonomer isethylene, 1-butene, 1-hexene or 1-octene. The stereo-regular (isotacticor syndiotactic) sequence or block content of the polymers imparts aheterophase (partial amorphous and partial crystalline) character ofcrystallizable content to the polymers. As used herein and as applied tosemi-crystalline heterophase copolymers, the term “crystallizable”describes those polymer sequences or blocks that can crystallize uponcooling. Crystalline content of the solidified semicrystallinecopolymers increases the cohesive strength of the hot melt adhesives.Hot melt adhesive formulations based on metallocene polymerizedsemicrystalline copolymers can eventually build sufficient crystallinecontent over time to achieve good cohesive strength in the formulation.

The second heterophase polymer comprises crystallizable polymer blocksor sequences, preferably of stereoregular sequences of polymerizedmonomer such as ethylene or propene, which sequences are long enough tocrystallize, typically at least repeating or block monomer units persequence.

In preferred embodiments, the crystallizable segments can bestereoregular or isotactic. Isotacticity of the olefin sequences can beachieved by polymerization with the choice of a desirable catalystcomposition. The Isotacticity is conventionally measured using DSC orC-13 NMR instrumental techniques.

The heterophase polymer has a crystallinity of at least 5 wt. %, 10 wt.%, 20 wt. %, 40 wt. % or 50 wt. %, preferably between 20% and 80%, morepreferably between 25% and 70%.

The heat of fusion of the heterophase copolymers (by ASTM E793) is about10 J/g to about 70 J/g and about 15 J/g to about 70 J/g, with a meltingpoint less than 150° C. and about 105° C. to about 135° C.

The heterophase polymer has a weight average molecular weight (Mw) ofabout 20,000 or less, preferably about 10,000 or less, preferably about500 to 8,000.

The heterophase copolymer has a viscosity of less than 20,000 mPa·s (1centipoise [cps]=1 mPa·s), for example less than 15000 mPa·s, in certainapplication less than 10,000 mPa·s and less than 5,000 mPa·s whenmeasured at 190° C. using a Brookfield viscometer (as measured by ASTM D3236) which is also referred to herein as “viscosity” and/or “Brookfieldviscosity.”

Some examples of heterophase polymers useful in the hot melt adhesivecompositions of include polyolefin such as polyethylene, polypropylene,and copolymers thereof such as polypropylene based elastomers sold byExxonMobil Chemical of Houston, Tex. under the trade name VISTAMAXX™ andpolyethylene based elastomers such as those sold by Dow Chemical Companyof Midland, Mich. under the trade names AFFINITY™ and ENGAGE™.

Other heterophase polymers that are useful in the hot melt adhesivecompositions include the polyolefin elastomers VISTAMAXX™ 8816,VISTAMAXX™ 2230, and ENGAGE™ 8200. AFFINITY™ GA 1900 has a density of0.870 g/cm³ according to ASTM D792, heat of fusion of 46.1 J/g, and aBrookfield viscosity of 8200 cP at 177° C. according to ASTM D 1084.AFFINITY™ GA 1950 has a density of 0.874 g/cm³ according to ASTM D792,heat of fusion of 53.4 J/g, and a Brookfield viscosity of 17,000 cP at177° C. according to ASTM D 1084. ENGAGE™ 8200 has a density of 0.87g/cm³ according to ASTM D792 and a melt index of 5 g/10 min at 190° C.These olefin elastomers are compatible with the propylene copolymersuseful in the hot melt adhesive compositions and improve physicalproperties such as low temperature adhesive performance withoutsacrificing effective set time.

Any conventional polymerization synthesis processes may prepare thepolyolefin copolymers. Preferably, one or more catalysts, which aretypically metallocene catalysts or Zeigler-Natta, catalysts, are usedfor polymerization of an olefin monomer or monomer mixture.Polymerization methods include high pressure, slurry, gas, bulk,suspension, supercritical, or solution phase, or a combination thereof,preferably using a single-site metallocene catalyst system. Thecatalysts can be in the form of a homogeneous solution, supported, or acombination thereof. Polymerization may be carried out by a continuous,a semi-continuous or batch process and may include use of chain transferagents, scavengers, or other such additives as deemed applicable. Bycontinuous is meant a system that operates (or is intended to operate)without interruption or cessation. For example a continuous process toproduce a polymer would be one where the reactants are continuallyintroduced into one or more reactors and polymer product is continuallywithdrawn. In one embodiment, the propene copolymer described herein isproduced in a single or multiple polymerization zones using a singlepolymerization catalyst. The heterophase polymers are typically madeusing multiple metallocene catalyst blends that obtain desiredheterophase structure.

The compositions disclosed herein can also comprise a plasticizer orplasticizing oil or extender oil that may reduce viscosity or improvetack properties in the adhesive. Any plasticizer known to a person ofordinary skill in the an may be used in the adhesion compositiondisclosed herein. Nonlimiting examples of plasticizers include olefinoligomers, low molecular weight polyolefin such as liquid polybutene,low molecular weight non-aromatic polymers (e.g. REGALREZ 101 fromEastman Chemical Company), phthalates, mineral oils such as naphthenic,paraffinic, or hydrogenated (white) oils (e.g. Kaydol oil or ParaLuxoils (Chevron U.S.A. Inc.)), vegetable and animal oil and theirderivatives, petroleum derived oils, and combinations thereof. Lowmolecular weight polyolefin may include those with Mw as low as 100, inparticular, those in the range of from about 100 to 3000, in the rangeof from about 250 to about 2000 and in the range of from about 300 toabout 1000.

In some embodiments, the plasticizers include polypropylene, polybutene,hydrogenated polyisoprene, hydrogenated polybutadiene, polypiperylene,copolymers of piperylene and isoprene, and the like, having averagemolecular weights between about 350 and about 10,000. In otherembodiments, the plasticizers include glyceryl esters of the usual fattyacids and polymerization products thereof a polymer of isobutylene. Apreferred plasticizer comprises a polyisobutylene polymer. The polymercan comprise major proportion of isobutylene units or can be representedas:[—C(CH₃)₂—CH₂—]_(n);wherein n=15 to 75. Polyisobutylene materials are viscous liquids withmolecular weight of about 200-20,000, about 200-5,000 or about500-2,000. The preferred materials have a Saybolt Universal seconds(SUS) viscosity at 100° C. of about 100 to 20,000. The characteristicfeatures of polyisobutylene are low gas permeability and high resistanceto the action of acids, alkalis, and solutions of salts, as well as highdielectric indexes. They degrade gradually under the action of sunlightand ultraviolet rays (the addition of carbon black slows this process).In industry, polyisobutylene is produced by ionic (AlCl₃ catalyzed)polymerization of the monomer at temperatures from −80° to −100° C.;they are processed using the ordinary equipment of the rubber industry.Polyisobutylene combines easily with natural or synthetic rubbers,polyethylene, polyvinyl chloride, and phenol-formaldehyde resins.

As noted above, embodiments of preferred compositions are made withsubstantially less than 40 wt. %, less than 20 wt. % or aresubstantially free of an effective amount of a conventional tackifiermaterial that can add any aspect of open time, substrate wetting or tackto the adhesive material. Avoiding the use of a tackifier reducesadhesive density, adhesive and product costs and frees formulators fromthe use of materials in short supply. Further, tackifier can impartundesirable odor in disposable articles and can also act as carriers oflow molecular weight plasticizers (like process oils that are used inSBC based adhesives) that can weaken the polyethylene back sheetmaterials used in baby diapers. Back sheet integrity is becoming moreimportant due to the downsizing of the polyethylene film thickness usedin these articles. By the term “conventional tackifier resins”, thoseresins commonly available in the adhesive art and industry that are usedin typical hot melt adhesives. Examples of conventional tackifing resinsincluded in this range include an aliphatic hydrocarbon resins, aromaticmodified aliphatic hydrocarbon resins, hydrogenated poly-cyclopentadieneresins, poly-cyclopentadiene resins, gum rosins, gum rosin esters, woodrosins, wood rosin esters, tall oil rosins, tall oil rosin esters,poly-terpene, aromatic modified poly-terpene, terpene-phenolic, aromaticmodified hydrogenated poly-cyclopentadiene resins, hydrogenatedaliphatic resins, hydrogenated aliphatic aromatic resins, hydrogenatedterpene and modified terpene and hydrogenated rosin esters. Often inconventional formulations such resins are used in amounts that rangefrom about 40 to about 65 wt. %.

In further embodiments, the compositions disclosed herein optionally cancomprise an antioxidant or a stabilizer. Any antioxidant known to aperson of ordinary skill in the art may be used in the adhesioncomposition disclosed herein. Non-limiting examples of suitableantioxidants include amine-based antioxidants such as alkyl diphenylamines, phenyl-naphthylamine, alkyl or aralkyl substitutedphenyl-naphthylamine, alkylated p-phenylene diamines,tetramethyl-diaminodiphenylamine and the like; and hindered phenolcompounds such as 2,6-di-t-butyl-4-methylphenol;1,3,5-trimethyl-2,4,6-tris(3′,5′-di-t-butyl-4′-hydroxybenzyl)benzene;tetrakis[(methylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate)]methane(e.g., IRGANOXTM1010, from Ciba Geigy, New York);octadecyl-3,5-di-t-butyl-4-hydroxycinnamate (e.g., IRGANOXTM 1076,commercially available from Ciba Geigy) and combinations thereof. Whereused, the amount of the antioxidant in the composition can be from aboutgreater than 0 to about 1 wt %, from about 0.05 to about 0.75 wt %, orfrom about 0.1 to about 0.5 wt. % of the total weight of thecomposition.

In further embodiments, the compositions disclosed herein optionally cancomprise an UV stabilizer that may prevent or reduce the degradation ofthe composition by radiation. Any UV stabilizer known to a person ofordinary skill in the art may be used in the adhesion compositiondisclosed herein. Non-limiting examples of suitable UV stabilizersinclude benzophenones, benzotriazoles, aryl esters, oxanilides, acrylicesters, formamidine carbon black, hindered amines, nickel quenchers,hindered amines, phenolic antioxidants, metallic salts, zinc compoundsand combinations thereof. Where used, the amount of the UV stabilizer inthe composition can be from about greater than 0 to about 1 wt. %, fromabout 0.05 to about 0.75 wt. %, or from about 0.1 to about 0.5 wt. % ofthe total weight of the composition.

In further embodiments, the compositions disclosed herein optionally cancomprise a brightener, colorant or pigment. Any colorant or pigmentknown to a person of ordinary skill in the art may be used in theadhesion composition disclosed herein. Non-limiting examples of suitablebrighteners, colorants or pigments include fluorescent materials andpigments such as triazine-stilbene, coumarin, imidazole, diazole,titanium dioxide and carbon black, phthalocyanine pigments, and otherorganic pigments such as IRGAZINB, CROMOPHTALB, MONASTRALB, CINQUASIAB,IRGALITEB, ORASOLB, all of which are available from Ciba SpecialtyChemicals, Tarrytown, N.Y. Where used, the amount of the brightener,colorant or pigment in the composition can be from about greater than 0to about 10 wt %, from about 0.01 to about 5 wt %, or from about 0.1 toabout 2 wt % of the total weight of the composition.

The compositions disclosed herein may also optionally comprise afragrance such as a perfume or other odorant. Such fragrances may beretained by a liner or contained in release agents such as microcapsulesthat may, for example, release fragrance upon removal of a release linerfrom or compression on the composition.

In further embodiments, the compositions disclosed herein optionally cancomprise filler. Any filler known to a person of ordinary skill in theart may be used in the adhesion composition disclosed herein.Non-limiting examples of suitable fillers include sand, talc, dolomite,calcium carbonate, clay, silica, mica, wollastonite, feldspar, aluminumsilicate, alumina, hydrated alumina, glass bead, glass microsphere,ceramic microsphere, thermoplastic microsphere, barite, wood flour, andcombinations thereof. Where used, the amount of the filler in thecomposition can be from about greater than 0 to about 60 wt. %, fromabout 1 to about 50 wt. %, or from about 5 to about 40 wt. %

TABLE 1 Exemplary and Useful Substantially Tackifier Free AdhesiveCompositions Component Embodiment Wt. % Wt. % Wt. % Amorphous REXTAC E6590-10 20-80 70-40 polymer Heterophase Vistamaxx 10-90 80-20 40-70polymer Plasticizer Polyisobutylene  0-40  5-35  5-30 AdditiveAntioxidant/stabilizer  0-20  1-20  1-15

One substantial advantage in the claimed adhesives relates to a densityof the adhesive formulations. Conventional tackifier is at a densitythat often ranges from about 1.07-1.09 g-cm⁻³. Conventional formulatedadhesives containing a conventional tackifier in amounts of about 40 to60 wt. %, have a density greater than 0.9 g-cm⁻³ or more. The formulatedadhesives of the invention, substantially free of tackifier, havedensities less than 0.9 g-cm⁻³, often in the range about 0.85-0.89g-cm⁻³ often 0.86-0.87 g-cm⁻³. Not only are these adhesives free of theproblems arising from tackifier materials, but the use of the claimedadhesives, and a lower density, permits the use of a reduced amount whenmeasured by weight, resulting in cost savings.

The hot melt adhesive compositions have melt rheology and thermalstability suitable for use with conventional hot melt adhesiveapplication equipment. The blended components of the hot melt adhesivecompositions have low melt viscosity at the application temperature,thereby facilitating flow of the compositions through a coatingapparatus, e.g., coating die or nozzle, without resorting to theinclusion of solvents or extender oil into the composition. Meltviscosities of the hot melt adhesive compositions are between 1500 cPand 3500 cP or about 2000 cP to 3000 cP in mille Pascal-seconds orcentipoise (cP) using a Brookfield thermosel RVT viscometer using arotor number 27 at 176.66° C. (50 rpm, 350° F.). The hot melt adhesivecompositions have a softening point (ASTM D 3461-97 Standard Test Methodfor Mettler Softening Point Method) of about 80° C. to 140° C., in someembodiments about 115° C. to 130° C. For certain applications, the hotmelt adhesive compositions have effective set times of about 5 secondsor less, for example about 0.1 second to 5 seconds, in embodiments about0.1 second to 3 seconds, and in some embodiments about 0.2 second to 1second. The effective set time of the hot melt adhesives areunexpectedly short, particularly given that the open time remains in theacceptable range.

Typical but non-limiting industrial applications of the hot meltadhesive compositions include packaging, particularly for lowtemperature use such as for dairy products or for freezer packaging offood products, and in sanitary disposable consumer articles, forexample, diapers, feminine care pads, napkins, etc. Traditional end useapplications such as book-binding, wood working and labeling will alsobenefit from both the low temperature flexibility, heat resistance andthe efficiency of end use in automated means of applying the hot meltadhesive compositions to various substrates.

Articles include items having any two or more substrates adhesivelybonded by a hot melt adhesive composition. Articles include cartons,boxes, envelopes, comestibles containers, books, magazines, disposablearticles such as diapers or feminine napkins, and the like. Thesubstrates that are adhesively bonded in such articles are formed frommaterials such as cardboard, paper, wood, aluminum, tin, steel,thermoplastics such as polyesters such as polyethylene terephthalate,polyamides such as nylons, or polypropylene, thermoset polymers, glass,ceramics, and combinations, blends, or layered composites thereof andinclude, in some embodiments, coatings of wax, acrylate polymers, orother materials; colorants, preservatives, stabilizers, processinglubricants, and the like as well as combinations of any of thesematerials. The substrates include solid, nonporous items and sheets aswell as porous items and sheets, such as nonwoven fabrics, paper, cottonbatting, and the like.

Another aspect is methods of manufacture employing the hot melt adhesivecompositions. The method involves application of the molten compositionsto a substrate, followed by contact of the adhesive composition with asecond substrate within 0.1 second to 5 seconds after application of theadhesive composition to the first substrate, wherein the contactingresults in an adhesive bond between the substrates.

Yet another aspect is an article of manufacture including the hot meltadhesive compositions, wherein the article includes at least twosubstrates adhesively bonded by an amount of a hot melt adhesivecomposition. Typical articles of manufacture include packaged goods,particularly packaged goods intended for low temperature use such as indairy products or for freezer packaging of food products; sanitarydisposable consumer articles, for example, diapers, feminine care pads,napkins, and the like; books and magazines; labeled articles; woodarticles such as furniture; and articles formed from a combination oflow energy and higher energy materials, for example a cardboard boxhaving a polyethylene wrap and/or a polypropylene label, or a wood frametable having a protective plastic top. In general, articles that areadvantageously bonded using the hot melt adhesive compositions benefitfrom both the low temperature flexibility, heat resistance and theefficiency of end use in automated means of applying the adhesivecompositions to substrates.

Hot melt adhesive compositions were formulated by melt blending asdescribed below, wherein specific components and amounts of thecomponents are shown below. In the articles manufactured using theadhesives, the articles can be manufactured by forming an adhesive bondbetween a polymer film and a fiber or fiber mass. The article can alsocomprise an adhesive bond formed between a polymer film and a nonwovenfabric. Additionally the article can be manufactured by forming anadhesive bond between a multi layer structure comprising the exteriorlayer of a polymer film and interior components comprising a fiber mapor a nonwoven fabric.

The adhesive materials can be used as a construction adhesive inassembly of commonly available consumer disposal articles. Such articlesinclude infant diapers, adult diapers, bed pads, sanitary products, andother absorbent articles. Combining at least a polymer film with otherfilms and fibrous materials typically makes these articles. Fibrousmaterials can include fabrics such as woven or nonwoven fabrics, fibersin the form of fiber vats, fiber collections, fiber balls, etc.

Such absorbent articles typically comprise an absorbent held within thearticle. The absorbent is usually covered using a nonwoven inner liner.Such liners comprise a highly permeable material such as a spunbondednonwoven structure that passes fluids or moisture from the interior ofthe article into the absorbent layer. The absorbent layer or structureformed within the absorbent article typically comprises a fiber mass pador cellulosic or wood pulp for the purpose of substantially absorbingliquid or fluid materials released into the absorbent article. The fiberor fluff can comprise a cellulosic fiber, a synthetic fiber or mixturesthereof such as blends of wood fiber, cellulosic fiber, polyethylenefiber, polypropene fiber or other fiber materials often including asuper absorbent material. Super or highly absorbent materials are usedto increase the absorptive capacity of the absorbent article. Suchmaterials are organic materials including modified natural gums andresins but often include synthetic polymer materials such as hydrogels.Carboxy-methyl Cellulose, alkaline metal salts of acrylic polymers,polyacrylamides, polyvinyl alcohol, polyethylene anhydride polymers andcopolymers, polyvinyl ether polymers and copolymers, hydroxyalkylcellulose polymers and copolymers, polyvinyl sulfonic acid polymers andcopolymers, polyacrylic polymers, polyvinyl-pyrrolidone polymers andcopolymers can be used in the absorbent function.

Nonwoven fabric layers used in such disposal articles typically aregenerally planar structures comprising a bonded assembly of natural orsynthetic fiber.

Such nonwoven materials are often made using a variety of techniques,including spunbonding, melt bonding, etc. Such nonwoven materials areoften manufactured by randomly placing fibers or rovings in asubstantially random pattern and are then thermally bonded usinginherent bonding characteristics of the fibers or by bonding the fibersusing resin materials applied to the fibers. Various polymers can beused to make nonwoven materials including poly olefins, polyesters,ethylene vinyl acetate polymers, ethylene acrylic acid polymers andothers.

The exterior of the article often comprises a polymer film that isliquid impervious. In certain aspects exterior polymer films can befurther modified using additional exterior layers to obtain a more clothlike or nonwoven character to the exterior polymer film. The exteriorfilm typically comprises a single layer of a polymer film but can be amulti-layer film structure. Typical polymer sheet materials comprisehigh tensile strength polymers including polyesters, poly olefins orother thermoplastic sheet materials that can be formed into film layers.The polyolefin or polyester polymer materials are often formed intosheets and are treated to improve strength, flexibility and punctureresistance. Techniques including biaxial orientation, heat treatment orsurface treatment can improve the film characteristics of the polymerfilms. Such polymer films often have a thickness that ranges from aboutten to about one hundred microns.

One embodiment of an absorbent article that we have mentioned comprisesthe impervious polymer film, an absorbent layer pad or mat and anonwoven interior layer. This three component structure is assembledusing the adhesive that is applied using manufacturing techniques thatadheres the nonwoven interior layer to the polymer film while holdingthe absorbent layer there between.

The adhesive compositions can be applied under melt conditions to asubstrate as a hot melt adhesive or may be coated, applied or sprayedonto the polymer film nonwoven or absorbent pad. Spray-on adhesives aretypically applied using slot coat, spray on or atomizing character in abead, dot pattern, spiral pattern or other conventional pattern usingsuch Nordson application techniques. In a preferred embodiment, thecomposition of the adhesive composition is applied to a substrate usinga slot coat (using Nordson true coat or Speed coat slot) at increasedmachine speed.

The material is typically applied in an amount of about 1 to about 100or about 4 to about 90 or about 7 to about 70 grams per square meter(g-m⁻²) of resulting bonded material. The adhesive materials can be usedfor disposal diaper and napkin construction elastic attachment anddisposal goods particularly preferred applications include baby diaperconstruction, diaper chassis construction, diaper core stabilization,diaper outer cover lamination, feminine napkin core stabilization,feminine napkin adhesive strip.

EXPERIMENTAL

A number of hot melt adhesive compositions were prepared by blendingfirst amorphous copolymer, second heterophase copolymer, polymerplasticizer/diluent and antioxidant under mixing conditions at elevatedtemperatures to form a fully homogenized fluid melt. Mixing temperaturesvaried from about 135 to about 200° C. preferably about 150 to about175° C. A WiseStir® mixer was used to ensure full homogenization ofcomponents into a final adhesive composition.

Examples 1-4

Hot melt adhesive compositions were formulated by melt blending asdescribed below, wherein specific components and amounts of thecomponents are shown in the following table 2.

TABLE 2 Exemplary Adhesive Formulations Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5Ex. 6 Ex. 7 Ex. 8 Source Component wt. % wt. % wt. % wt. % wt. % wt. %wt. % wt. % ExxonMobil Chemical, Vistamaxx 8816 20 35 35 35 15 15 15 10Houston, TX Huntsman Chemicals Rextac E-65 59.5 60 55 50 64.5 59.5 59.559.5 Ineos Chemicals Indapol H-300 20 4.5 9.5 14.5 20 24.99 0 0(polyisobutylene) (Polyisobutylene) Ineos Chemicals Indapol H-1900 0 0 00 0 0.5 24.99 29.99 (Polyisobutylene) Ciba Geigy Ltd., Irganox 1010 0.50.5 0.5 0.5 0.5 0.5 0.5 0.5 Basel, Switzerland (Hindered Phenol) Mayzo,Inc. Fluorescent Benetex OB 0 0 0 0 0 0.01 0.01 0.01 Ooptical Brightener

TABLE 3 EXEMPLARY ADHESIVE VISCOSITY DATA Brookfiled Viscosity @ Ex. 1Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 121.1° C. (250° F.) 2620029750 16600 39000 135° C. (250° F.) 7710 12125 9725 7500 8425 7100 91008750 148.9° C. (250° F.) 4675 6350 5325 4525 5150 4200 5325 5375 162.8°C. (250° F.) 3075 4190 3500 2980 3475 2800 3550 3375 176.7° C. (250° F.)2220 2945 2450 2080 2315 1920 2.385 2275 Mettler Softening Point 121° C.125° C. 125° C. 124° C. 120° C. 118° C. 118° C. 115° C. Density g-cm⁻³0.86-0.87 0.86-0.87 0.86-0.87 0.86-0.87 0.86-0.87 0.86-0.87 0.86-0.870.86-0.87 ASTM 792

These data indicates that the materials will provide excellentconstruction bonding in disposable absorbent articles. Note viscosityrelates to the resistance to flow of the material under certainconditions. This distinctive property determines the flowability, degreeof wetting, and penetration of the substrate by the molten polymer. Itprovides an indication of its processability and utility as a hot meltadhesive material. Melt viscosity is generally directly related to apolymer molecular weight and is reported in Millipascal-second's orcentipoise (cP) using a Brookfield thermosel RVT viscometer using arotor number 27 at the stated temperature.

Mettler softening point in degrees Centigrade or degrees Fahrenheit istypically measured using ASTM D3104. The amorphous nature of the polyolefin materials results in a melting point, which is not sharp ordefinite. Rather as the temperature increases, amorphous polymersgradually change from a solid to a soft and then to a liquid material.No clearly defined glass transition or melting temperature is oftennoted. This temperature testament that generally measures the precisetemperature at which a disc of polymer sample, heated at a rate of 2° C.per minute or 10° per minute becomes soft enough to allow the testobject, a steel ball (grams) drops through the sample. The softeningpoint of a polymer reported in degrees Centigrade or degrees Fahrenheitis important because it typically indicates the polymer's heatresistance, useful application temperatures and solidification points.

The claims may suitably comprise, consist of or consist essentially of,or be substantially free of any of the disclosed or recited elements.The invention illustratively disclosed herein can also be suitablypracticed in the absence of any element which is not specificallydisclosed herein. The various embodiments described above are providedby way of illustration only and should not be construed to limit theclaims attached hereto. Various modifications and changes may be madewithout following the example embodiments and applications illustratedand described herein, and without departing from the true spirit andscope of the following claims.

What is claimed is:
 1. An absorbent article comprising a liquidpermeable interior layer, a liquid impervious exterior layer, and anabsorbent layer therebetween; further comprising a hot melt adhesivecomposition consisting essentially of: (i) about 90 to 10 wt. % of anamorphous polyolefin copolymer composition comprising 50 to 70 wt. %1-butene; (ii) about 10 to 90 wt. % of a heterophase polypropylenecopolymer composition comprising propene and a comonomer comprisingethylene, 1-hexene or 1-octene and comprising amorphous character andcrystalline blocks; and (iii) about 0.1 to 30 wt. % of a polyisobutyleneplasticizer made with an AlCl₃; wherein the adhesive provides cohesivestrength from the heterophase polypropylene copolymer and adhesivestrength from the amorphous polyolefin copolymer.
 2. The absorbentarticle of claim 1, wherein the interior layer comprises a nonwoven. 3.The absorbent article of claim 1, wherein the absorbent layer comprisesa super absorbent material.
 4. The absorbent article of claim 1, whereinthe exterior layer comprises a polymer film.
 5. The absorbent article ofclaim 4, wherein the exterior layer comprises a multi-layer structure.6. The absorbent article of claim 4, comprising another exterior layercomprising a nonwoven layer.
 7. The absorbent article of claim 1,wherein the article comprises an adhesive bond between a polymer filmand a nonwoven fabric.
 8. The absorbent article of claim 1, wherein thearticle comprises an adhesive bond between the interior layer comprisinga nonwoven and the exterior layer comprising a multi-layer structurecomprising a polymer film.
 9. The absorbent article of claim 1, whereinthe hot melt adhesive bonds the interior layer and the exterior layer.10. The absorbent article of claim 1, wherein the adhesive may becoated, applied, or sprayed onto either a nonwoven or polymer film layerof the article.
 11. The absorbent article of claim 1, wherein thearticle is selected from the group consisting of infant diapers, adultdiapers, and feminine care pads.
 12. The absorbent article of claim 1,wherein the heterophase polypropylene copolymer comprises at least about5 wt. % crystalline sequences or blocks.
 13. The absorbent article ofclaim 1, wherein the heterophase polypropylene copolymer comprisesgreater than 40 wt. % of propene and less than 60 wt. % of the comonomerand has a crystallinity of greater than 10%.
 14. The absorbent articleof claim 1, wherein the adhesive is substantially free of a tackifier.15. The absorbent article of claim 1, wherein there is about 50 to 80wt. % of the amorphous polyolefin copolymer and about 10 to 50 wt. % ofthe heterophase polypropylene copolymer.